A Solution Method for Tunnel Supporting Structure System Incorporating the Active Control of Surrounding Rock Deformation

With the continuous deepening that humans exploit underground space, tunnel engineering passing through sensitive strata, e.g., ultralarge buried depth, high water pressure, and active faults, has become more frequent. However, the current tunnel-supporting concept emphasizes the passive regulation effect of the primary support and the secondary lining on the surrounding rock deformation and ignores the principle of fully utilizing the self-bearing capacity of the surrounding rock in the New Austrian Tunneling method. Therefore, the current supporting system is not ideal for controlling the deformation under these sensitive strata, and it is imperative to propose an active supporting system that can mobilize the surrounding rock to be self-supporting. In this paper, through mathematically analyzing the deformation monitoring data of 203 tunnel sections, a deformation control benchmark under the active deformation control concept is proposed. The deformation control effect of the prestressed rock bolt is obtained based on field measurements and numerical calculations. Furthermore, the proposed virtual supporting force method is used to solve the range and parameters required for advanced support. Finally, the active supporting parameters satisfying the deformation control benchmark are obtained by using the elastic–plastic theory. The results show that the established deformation control benchmark can be used to evaluate the active supporting parameters. On this basis, the solving method for the active supporting system and its parameter are constructed. By adopting this method, the suitable forms and parameters of the prestressed rock bolt and the range and parameters of the advanced support in different geological environments are obtained. Finally, the composition forms and parameters of the active supporting systems with different lithologies and different buried depths are proposed.